The present invention is related to resin-type ion exchange devices. Resin-type ion exchange devices have many uses such as the softening of water, deionization of sugar compounds and processing of protein complexes. As the fluid to be processed is passed through a tank containing an ion exchange resin, ions in the fluid to be processed are exchanged with ions found in the resin, thereby removing objectionable ions from the fluid and exchanging them for less objectionable ions found in the resin. During this process the ability of the resin to exchange ions is gradually reduced. That is, as the resin captures the objectionable ions and releases the less objectionable ions, its capacity to continue this exchange process is gradually exhausted. Eventually, a steady state is reached in which no further objectionable ions in the fluid to be processed can be exchanged for the less objectionable ions found in the resin. The point at which this state is reached can be estimated generally from the concentration of the objectionable ions found in the fluid to be processed, the volume of fluid to be processed passing through the ion exchange resin device, the relative chemical activities of the objectionable and less objectionable ions, and other factors. Once this point is reached, the resin can no longer remove the objectionable ions from the fluid to be processed.
It is known in the art of ion exchange resin devices to regenerate the ion exchange resins by chemically removing the objectionable ions from the resin and replacing these with the less objectionable ions. This regeneration process requires the suspension of the ion exchanging process. During this regeneration process, a substance having a high concentration of the less objectionable ions is applied to the ion exchange resin. Because this produces a new balance of concentrations between the respective ions, the ion exchange resin now exchanges the objectionable ions captured during the ordinary process for the less objectionable ions applied during regeneration. As a result of this process, the ability of the ion exchange resin to remove objectionable ions from the fluid to be processed is regenerated. At the same time as the ion exchange resin is regenerated, the device may perform other functions such as backwashing the resin tank in order to remove trapped particulate matter, rinsing the resin tank to remove soluble materials and application of a sterilization agent to prevent bacterial growth.
Since this process of regeneration of the ion exchange resin renders the ion exchange device inoperable and since the ability of the ion exchange device to remove the objectionable ion is controlled in large part by the state of the ion exchange resin, it is most important that the regeneration process be undertaken at appropriate times. Too frequent regeneration of the ion exchange resin leads to unnecessarily rendering the ion exchange device inoperable as well as unnecessary use of energy and materials during the regeneration process. On the other hand, too infrequent regeneration of the ion exchange resins leads to an increase in the concentration of the objectionable ions at the output of the ion exchange device during the periods in which the capacity of the ion exchange resin is substantially exhausted.